Tracing apparatus



I GO l J. M. MORGAN, JR

TRACING APPARATUS Original Filed Dec.

JOHN M. MORGAN JR.

HIS ATTORNEY May 24, 1960 United States Patent vided and thisapplication Oct. 13, 1958, Ser. No. 766,968

2 Claims. CI. 90-62) This'invention relates to a tracing head for atracer control system and, more particularly, to a tracing head providedwith a tracing finger adapted to follow the pattern being traced andproduce electrical signals which are indicative of the over-deflectionor underdeflecti'on of the finger by the pattern.-

This application is a division of my co-pending patent applicationSerial No. 477,976 for Tracing Apparatus filed December 28, 1954, nowPatent No. 2,868,087 issued Ianuary 13, 1959.

The tracing head and finger forming the subject matter of the presentinvention ia're adapted to sense deviations in the path followed bythetracing head from the outline of the pattern in both a contouring planeand also in a direction normal thereto so as to provide full3-dimensional tracing of the pattern by the tracing apparatus.Accordingly, the tracing head is provided with one signal producingmeans which senses deflection of the tracing finger for 360 tracing inthe contouring plane, and with another signal producing means whichsenses deflections of the finger in a direction at right angles to thecontouring plane. The unique construction of the tracing head whichpermits the simultaneous production of these two signals will behereinafter described in greater detail.

' It is therefore an object of the present invention to provide a3-dimensional tracing head having a single tracing finger arranged tosimultaneously produce both depth and 360 tracing signals.

- Another object of the invention is to provide a tracing head having atracing fingersupported for both lateral and axial deflections by thepattern and, adapted to produce simultaneously one signal which isindicative of lateral'defiections of the finger by the pattern, andanother signal which is indicative of axial deflections of the fingerthereby.

With these and other objects in view which will become apparent from thefollowing description, the invention includes certain novel features ofconstruction and combinations of parts, the essential elements of whichare set forth in the appended claims, and a preferred form or embodimentof which will hereinafter be described with reference to the drawingswhich accompany and form a part of this specification.

Referring to the drawings in which like reference numerals indicate likeor similar parts:

Fig. l is a cross-sectional elevation of the tracing head as viewed fromthe rear.

Fig. 2 is a left side view of the tracing head with the cover removed.

Fig. 3 is a right side view of the tracing head with the cover removed.

The tracing head herein disclosed is particularly suitable for use in atracing system of the type described in my co-pending patent applicationSerial No. 477,976 although its utility is not necessarily limited to atracing system utilizing a non-directional type of tracer as showntherein. The instant tracing head could equally well be adapted for useas a directional type of tracer by making provision for rotating thehead in synchronism with the direction controlling mechanism for thefeed motors, and by introducing a suitable amount of eccentricity to thetracing finger as is well known in the tracer art. The novelty in thepresent tracing head resides in the particular means utilized forsimultaneously producing both 360 and depth signals from a singletracing finger. For this purpose, the tracing head includes an outersleeve which is mounted for 360 tilting movement about its point ofsupport in the tracing head. Mounted for axial sliding movement withinthe sleeve is a stem or plunger which carries at its outer end a tracingfinger adapted to contact and follow the pattern to be traced. A 360signal pro: ducing device, or pickup, is supported by the tracing headand provides signals indicative of the degree of tilt of the sleeve andfinger relative to the head through a motion transmitting mechanismwhich connects the sleeve to a movable armature in the pickup. A secondsignal producing device, or pickup, is carried by the sleeve andprovides a second, or depth signal, which is indicative of the axialdisplacement of the stem relative to the sleeve. This is effected by aconnection between the stem and a movable armature carried by the secondpickup. The tracing head is thereby enabled to produce both signalssimultaneously as the finger is displaced both laterally and axially bythe pattern being followed. It is, of course, possible to select one orthe other of the signals for use if both are not needed for the type ofoperation being performed. That is, for 360 tracing only, the 360 signalmay be selected for use to the exclusion of the depth signal, while fordepth tracing only, the depth signal may be selected to the exclusion ofthe 360 signal.

The tracing head will now be described in greater detail in connectionwith a preferred embodiment of the invention which has been shown in theaccompanying drawings. As herein shown the head is housed in a box-likecasing having a pair of removable cover plates 116 and 117 for enclosingthe right and left sides thereof, respectively. Secured to the bottomofthe casing is.a cylindrical housing 118 in which is received the lowerend of a sleeve 119. This sleeve is supported at its lower end withinthe housing 118 by a shoulder 120 formed on ,a cap 121 secured to thebottom end of the housing, and also by a ball bearing 122 resting on topof the cap 121. Lying within the sleeve 119 is a tracing finger plunger123 which is mounted for longitudinal sliding movement within the sleeveby ball bearings 124 and 125. At its lower end, the plunger 123 isprovided with a chuck 126 for holding the tracing finger 134, while atits upper end, the plunger is fitted with a lateral extension 127, whichprojects through a slot provided in the sleeve 119.

The upper end of the sleeve 119 is fitted with a cap 130 provided with aconical seat in which is received a ball 131. Resting on the top of theball 131 is a sleeve 132 which, like the cap 130, is formed with aconical seat for engaging the ball 131. The sleeve is mounted for axialsliding movement within a cylindrical bore provided in a bushing 133received in an aperture provided in the top of the casing 115. Thesleeve 132 is guided for sliding movement within the bushing by means ofball bearings 134 and 135 and is spring urged downwardly into contactwith the ball 131 by a compression spring 136 lying inside the sleeveand bearing against a cover 137 fastened to the top of the bushing.Secured to the lower end of the sleeve 132 is an offset lateralextension 138 which will occupy its lowermost position when the tracingfinger 34 is in its undeflected, or Fig. 1 position. However, anysidewise pressure applied against the finger 34 will cause the sleeve119 to be rocked about its base and result in raising the sleeve 132 andextension 138.

As shown in Fig. 1, the extension 138 is connected to an armaturecarrier 142 so as to cause the carrier to partake of its up and downmovement in response to sidewise movement of the tracing finger. Theconnection between the extension and carrier includes a pointed screw140 threaded into a hole in the bottom of the carrier, and a springpressed plunger 141, also pointed, which bears against the upper face ofthe extension and maintains it in contact with the pointed end of screw140. The carrier 142 is made of nonmagnetic material and carries a softiron armature 145 (Fig. 3) which, together with an E-magnet 148, forms adifferential transformer 146. The E-magnet is mounted on a holder 147which is screwed fast to the casing 115 while the carrier is supportedfor vertical movement by a pair of reeds 143 and 144 fastened to theholder 147. In Fig. 3 the carrier is shown in the position which itoccupies when the tracing finger in undefiected wherein there is agreater overlap of the bottom pole than of the upper pole by thearmature. When the tracing finger 34 is deflected sufiiciently toequalize the overlap of the armature 145 with the poles of the E-magnet148, the magnetic circuit of the transformer will be balanced and, theerror signal from the tracing head will be zero. This, then, willrepresent what may be termed the normal or null position of the tracingfinger 34.

The carrier 142 also carries upper and lower brackets 150 and 151,respectively, the laterally extending arms of which are fitted withadjustment screws 152 and 153, respectively. The adjustment screws areadapted to cooperate with the operating'butto-ns of a pair of normallyclosed limit switches 154 and 155 supported on the casing 115. When thecarrier 142 is in the position shown in Fig. 3, that is, in the positionit occupies when the tracing finger 34 is undeflected, the adjustmentscrew 152 will hold the contacts of the switch 154 open but will permitthem to close upon slight upward movement of the carrier resulting frominitial deflection of the finger 34 by the pattern. Adjustment screw 153is spaced a sufiicient distance from the operating button of switch 155so as not to become effective to open the contacts of the switch untilthe carrier has been moved upwardly to a considerably degree. The limitswitches 154 and 155 serve to sense contact of the tracing finger withthe pattern and overdeflection of the tracing finger by the patternrespectively.

The extension 127 carried by the plunger 123 (Fig. 3) is adapted tocontrol the movement of an armature carrier 160 which, like the carrier142, is connected with the extension by a screw 161 engaging with thebottom of the extension and a spring pressed pin 162 engaging with thetop of the extension. The carrier will thereby be constrained to followthe movements of the extension 127 which moves up and down in responseto vertical movement of the tracing finger 34.

The carrier 160 is constructed of non-magnetic material and has embeddedtherein a soft iron armature 163 (Fig. 2) which lies adjacent the polefaces of an E-magnet 168 of a diiferential transformer 164. The E-magnetis mounted in a holder 165 supported on the sleeve 119 by a bracket 159pinned to the sleeve to which the holder is fastened by screws 158,while the carrier 160 is supported for translational movement by a pairof reeds 166 and 167 which are attached to the holder 165. In Fig. 2 thecarrier 160 is shown in the position it occupies when the tracing finger34 is in its lowermost position. When the carrier is in this position,the armature 163 lies below its centered position with respect to thepoles of the E-magnet 168. The carrier is urged toward this position bythe force of gravity acting on the plunger 123 which biases it towardthe position shown in Fig. 1 where the bottom edge of the piece on whichextension 127 is formed lies against the bottom edge of the slot formedin the sleeve 119. This defines the lowermost position of the plungerand upward pressure on the bottom of the tracing finger 34 will beeffective to raise the plunger and move the armature 163 upwardly towardthe centered position with respect to the poles of the E-magnet 168.

From the foregoing it will be noted that the tracing head 33 issensitive both to sidewise deflection of the tracing finger 34, whichcauses vertical movement of the extension 138, and also to verticaldisplacement of the finger, which causes vertical movement of theextension 127. Hence, the tracing head is of a three dimensionalcharacter, the extension 138 responding to horizontal deflections of thetracing finger from any direction within a full 360", and the extension127 responding to vertical deflections of the finger.

While I have described my invention in connection with one possible formor embodiment thereof, and have used, therefore, certain specific termsand language therein, it is to be understood that the present disclosureis illustrative rather than restrictive and that changes andmodifications may be resorted to without departing from the spirit ofthe invention as defined by the claims which follow.

I claim:

1. A tracing head for contour tracing apparatus comprising a frame, asleeve fulcrumed for rocking movement on said frame from anunderdeflected position through a null position to an overdefiectedposition, a spring biased element mounted on said frame for reciprocablemovement axially of said sleeve, means including a conical seat on theend of said sleeve, and a ball in said seat, for transforming therocking movement of said sleeve into reciprocatory movement of saidelement, an electrical pickup operable by said element to provide asignal signifying the position of said sleeve, relative to said frame, atracing finger plunger journaled in said sleeve for longitudinal slidingmovement therein from an underdeflected position through a null positionto an overdefiected position, an aperture in said sleeve, a lateralextension on said plunger projecting through said aperture, and anelectrical pickup connected with said extension for operation thereby toprovide a signal signifying the position of the plunger within saidsleeve.

2. The tracing head of claim 1 wherein said firstmentioned pickup issupported on said frame, and said second-mentioned pickup is supportedon said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS2,395,525 Wilkie et a1. Feb. 26, 1946 2,470,244 Fryklund May 17, 1949FOREIGN, PATENTS 512,234 Great Britain Aug. 30, 1939

